Articular cartilage

Type of hyaline cartilage covers the bone ends and makes smooth movements possible.

It distributes the load across joints,minimizing the peak stress on subchondral bone.

Relatively acellular. No vascular,neural or lymphatic supply Has little capacity to heal after injury. Wear resistant Low frictional Lubricated surface Slightly compressible and elastic

Differs from hyaline cartilage in that it is not covered by perichondrium. Collagen fibres of articular cartilage

matrix are of type-II which exhibit

characteristic cross banding of collagen fibres exsist.

Young cartilage – typically white,smooth,

glistening and compressible Aged – thinner,less cellular,firmer and

more brittle with less regular surface and yellowish opacity. Thickness – Bony end plate

ZONES OF ARTICULAR CARTILAGE 1) SUPERFICIAL ZONE Not smooth,layer of hyaluronic acid LAMINAR SPLENDENS –most superficial Elongated chondrocytes,relatively inactive 2) TRANSITIONAL ZONE Thicker ,cells rounded & larger, arranged

pairs Actively engaged in matrix component

synthesis

DEEP ZONE - Largest zone - Largest collagen fibrils,highest proteoglycan content, lowest water ZONE OF CALCIFIED CARTILAGE - Irregular cells pyknotic nuclei /stability - TIDE MARK - Continuous with subchondral plate

PERICELLULAR MATRIX - CHONDRON - Modulate the pressure transmission - regulation of chondrocyte response to pressure,prevent squashing TERRITORIAL MATRIX - Fibrillar basket - surrounds the pericellular matrix

INTERTERRITORIAL MATRIX - Largest matrix compartment - parellel arrangement of collagen

fibrils - responsible for mechanical

properties.

Less than 1% of tissue volume Rarely divide normally / cell density

decreases with age Synthesize matrix components-

proteoglycans constantly renewed,collagen

slow turnover CILIUM – Regulation of matrix turnover

COLLAGEN - Type II ,major (90%) - Characteristic cross banded fibrils - Type IX,X,XI minor NON-COLLAGENOUS PROTEINS - Link protein /binding GAG to hyaluronic

acid - Chondronectin and anchorinCII

PROTEOGLYCANS - Family of glycoproteins large protein

core attached to GAG side chains. - Form of large aggregates - Provide the resilience to A.C under

load

Mature A.C – diffusion from synovial fluid

Immature A.C – vascular channels in sub chondral bone,base of cartilage,S.F Energy – anerobic pathway Microenviroment:high CO2 & low O2 Survive for more than 2 days after

death

CHONDROMALACIA: A.C damage or degeneration OUTER BRIDGE Classification: Based on arthroscopic exam

GRADE O- Normal GRADE I- Swelling & softening of intact

A.C GRADE II-Fissuring & fibrillation over

small area < .5 inch GRADE III- Same over larger area > .5

inch GRADE IV- Erosion of subchondral bone

Mitosis induced by laceration,compression, Superficial lacerations – doesn’t cross tidemark

donot heal. Penetrates the subchondral bone- reach S.C vessels initiate healing process Fibrinous arcade – scaffold that directs the mesenchymal cells to form F.C matrix Repaired tissue – intermediate between H.C & F.C / poor biomehanical properties.

Biphasic material – solid & liquid phase Fibre reinforced gel- mutually repellant macromolecules binds water-osmotic P. Water resides in microscopic pores and

flow of the water induced by pressure

gradient or matrix contraction.Flow pressure provides load support & minimize

stress on matrix.

JT loading & motion required to maintain normal adult A.C Immobilisation of JT cause rapid loss of proteoglycans so deformation in

response to load will increase. Excessive use or increased loading

affect

Debridement of chondral flaps and removal

of loose chondral fragments. Abrasion chondroplasty Microfracture

Periosteal & Perichondrial grafting Autologous cartilage implantation Osteochondral autograft Osteochndral allograft